This invention relates to a coupling or combining process of two member to-be-coupled by the steps of arranging two members to-be-coupled so as to form an interspace between coupling faces of the two members, interposing a coupling member in the interspace and applying pressure in a cooling state to force the plastic or non-elastical flowing of the coupling member and more particularly a coupling process preferably used to strongly fix a shaft, plate, rod and cylindrical member made of metal or synthetic resin to each other.
There are welding including brazing and casting as methods to couple two members to-be-coupled by using a coupling member as a third member.
As is well known, welding causes thermal deformation owing to heating both member to-be-coupled and coupling member, so that a structure of high dimensional accuracy is difficult to obtain. In addition, there exists a limit in the selection of a material for the member to-be-coupled, the coupling member, electrode, brazing. Further, the welding is disadvantageous relative to productivity as well as to requiring large-scale facilities and being liable to occur faults in quality due to the dispersions of working conditions.
Also, with the casting process, the construction of equipment becomes complicated and larger in size due to the installation of an internal chill and a turning-preventing mechanism in order to ensure the coupling strength. Further, casting is disadvantageous the selection of materials for the coupling member is limited as well as productivity and accuracy.
There have also been known processes of inserting under pressure and of caulking in order to directly couple two members to-be-coupled.
As is well know, in the process of inserting in pressure there is a limit in strength and especially the produced products are weak to impacts. Further, this process has a defect in that it is difficult to obtain a required strength in a case of materials having less elongation such as casting iron.
With the process of caulking, there exists a limit in selection of materials for the members to-be-coupled and to be subjected to the caulking working; this means that materials having small deformation resistance must be selected. Thus, the sufficient coupling strength is not always obtained in any material construction, and especially it is impossible to obtain the sufficient coupling strength in a case of casting iron. Further, the caulking has a defect that the coupling strength is extreamly reduced, depending upon the employed temperature conditions, when there exists a large difference in the thermal coefficient of expansion of two members to-be-coupled.
Also, as a method to directly couple two members to-be-coupled, a method is know which comprises applying pressure on a first member to-be-coupled to force a part thereof to non-elastically flow in a groove formed on a second member to-be-coupled. However, in this method the part of the first member is not sufficiently inserted or bited into the groove and hence an interstitial gap between the first member and the surface of the groove occurs. This is due to a fact that when the pressure is applied on the end portion of the first member to-be-coupled by a metal mould, the generated stress in the end portion permits the deformation in the small constraint direction and it is impossible to give rise to a stress of such an extent of magnitude as induces a sufficient non-elastical deformation locally in only the groove part.
Moreover, a coupling process for coupling the members to-be-coupled by non-elastically deforming the coupling member interposed between the members to-be-coupled is also known.
U.S. Pat. No. 3,559,946 exists as prior art. According to this reference, each rectangular groove in section is formed on each coupling face of two members to-be-coupled and a coupling member is non-elastically deformed to force a part thereof to non-elastically flow. However, with this construction since the sectional figure of the groove is rectangular, after the coupling member has flown, an occurance of a gap between the surface of the groove and the flown coupling member cannot be avoided and hence acts to limit the strength of coupling force.
Further, U.S. Pat. No. 2,038,124 is known as another prior art. According to this reference, grooves which are semicircular in section are respectively formed on coupling faces of two members to-be-coupled, and a coupling member is given pressure for non-elastical deformation to be forced a part thereof to non-elastically flow into the grooves. However, with the construction the length of the coupling member is much larger than the width of a gap formed between the coupling faces of two members to-be-coupled and thus the given force is mainly consumed for friction generating between the coupling member and the members to-be-coupled within the gap. There exists a limit in magnitude of stress generated to force a part of the coupling member to non-elastically flow into the grooves. Accordingly, the large non-elastical flowing cannot be induced and hence, results to insufficiently fill the grooves by the coupling member.
Further, U.S. Pat. No. 2,804,679 is known as another prior art. According to this reference, two semicircular grooves are formed on a coupling face of a member to-be-coupled and a surface of the other member to-be-coupled is circular in section. According to this construction, since the grooves are formed on only one surface but not on the other surface, the large coupling force is not induced. Further, since the two grooves are in series, after a part of the coupling member has flown into a upper groove, a part of the coupling member is filled in a lower groove. Thus, the coupling member is given an action to be separated into a part remaining in the upper groove and another part flowing downwardly, so that a crack might be generated in the coupling member.
Further, U.S. Pat. No. 3,641,865 is known as another prior art. According to this reference, a groove being trapezoid in section is formed on a surface of a member to-be-coupled but not on the other surface of an opposite member to-be-coupled. According to this construction, since a groove is formed on only one surface but not on the other surface, large torque of cannot be transferred through the combination of two members to-be-coupled and a coupling member.